Process for the absorption of hydrogen sulphide and ammonia from gases



Oct.13, 1931. c. HANSEN 1,825,779

PRocEss Fon THE AssoRPTIoN oF HYDROGEN .SULPHIDE AND AMMoNIA FROM GAsEs original Filed June 18, 1927 v C/uisfian Hansen Afrom industrial gases by washing Patented oci. i3, i931 CHRISTIAN HANSEN, or 'EssEN-srAnTWALn, GERMANY, -AssieNon 'ro I.. FARBEN-l INDUSTRIE AKTIENGESELLSCHAFT, OF FRANKFOBT-ON-THE-MAIN, GERMANY,

CORPORATION F GERMANY PEocEss Eonl THE Ansoar'rioN 0E HYniaoeEN sULrHIDE AN'nAiiMoNIA Enom @Asi-3sl Original application led June 18, 1927, Serial No. 199,862, an'd in Germany-lilly 21, 1926.4 Divided and this application led June 1 9,

This present invention concerns the absorption of ammonia and hydrogen sulphide with solutions containing ammonium polythionate and ammonium lhiosulfate and is diagrammatically illustrated by the accompanying flow-sheet. The process is carried out in two stages, such that the ammonia, which for a part or wholly'is' separated before the washing process, is introduced in the second stage and in the rst stage suliicient hydrogen suli phide is precipitated as sulfur (if necessary and the polythionate:

with the addition of sulfurous acid) to makev available in the second stage more than two molecules of ammonia in respect of every one molecule of hydrogen sulphide to be removed. The process'gmay be carried out under increased pressure.

Hitherto it has` not been possible to carry out technically thev separation of ammonia and hydrogen sulphide for industrial gases by means of ammonium olytliionate solutions, since the velocity of tllije respective-react ons, in particular' that between hydrogen sulphide (NH4) 2S4O+ is too small. f v

In accordance with the present .invention the absorption proceeds suiiciently rapidly provided thatsuilicient ammonia is present to enable the following lreaction to occur:

(Name+ (Nnazsioyemnazszos-r s It does,'however, not suiice for causingthis reaction to take place, to add the requisite amount of ammonia in the proportion of two molecules of ammonia to one molecule of hydrogen sulphide, indicated in the equation, since the reaction only proceeds in neutral or: better still in weakly alkaline solutionf, The polythionate solutions in fact undergo a constant gradual spontaneous decomposition, with the result that the sulfurous acid thus set free combines with part of the addedam- 'monja to form sulfite or 'thiosulfate It follows that to obtain a quantitative conversion of the hydrogenl sulphide it will benecessary to add a corresponding quantity of ammonia for the regeneration of the wash liquors.

1928. Serial No. 286,712.-

parts of ammonia to 1 part of hydrogen sulas phide. N i

Now/coal gases do not contain suiiicient ammonia to comply with this ratio, and also the quantity of hydrogen sulphide no longer suilces to convert into ammonium sulfate the excess of ammonia over the ratio of two molecules .of ammonia to one molecule of hydrogen sulphide'which must therefore-be added inthe form of sulfur or sulfur dioxide. Further in accordance with my invention the separation of ammonia and hydrogen sulphide from industrial gases by means of polythionate and thiosulfate containing solutions can nevertheless be carried out technically with the quantities of ammonia and hydrogen sulphide available in the said gases by carrying out the process in two stages in suchamanner that a part of the ammonia or the whole ammonia is separated before the washing process and introduced in the second sta e. In the first stage the gas which comes from 51e ammonia absorption with a vtem erature of 25-30o C. is freed by washing wit polythio.

i nate and thiosulfate containing solution from hydrogen sulphide to the enxtent that in the second stage more than twogamolecules of ammonia are available for one molecule of the hydrogen sulphideY still to beremoved. The sulfur precipitated in the first stage supplements the quantity of sulfurous acid necessary The solutions produced in the absorption process, containing mainly ammonium thiosulfate are reconverted in the known'manner to polythionate by means of sulurous acid:

2 (NH4) 2S2O3 -l-BSOZ S=2 (NH4) 2Si06 mii-imszoffesoff .certain quantity of polythionate,besides thiothe wash liquor. 106

sulfate still remains in ratio of two molecules of 20. interchanged, with the result that a separate Likewise in the regenerationV the whole of the thiosulfate need not be converted into polythionate and the wash liquor thus after regeneration still contains thiosulfate.

In the first step sulfurous acid may also be added in a quantity corresponding to the medium amount of hydrogen sulphide, so that in this case the solution advantageously contains a little more thiosulfate than polythionate. The reaction then proceeds mainly according to the equation:

and is facilitated by the presence of thiosulfate. The unconverted portion of the sulfurous acid combines with the thiosulfate to form polythionate. By providing an excess' of sulfurous acid the Wash liquors produced in the first and secondr stages can be mutually regeneration becomes unnecessary, since in the first stage a solution containing an excess of polythionate is produced and in the second stage one containing an excess of thiosulfate.

The introduction of ammonia in the second `7stage can be eected jointly with the gas or directly to the liquid, in the latter case also in the form of aqueous ammonia.

The concentration of the liquor on account of thiosulfate and polythionate is kept as high as possible to avoid higher costs for evaporation.

The process can be carried out wholly or partially under superatmospheric pressure.

The working up of the wash liquors to amthe known manner.

This is a division of my copending application Ser. No. 199,862, of June 18, 1927.

Under theaterm stage used in the claims I understand one or several washing treatments, every stage using the same washing liquor.

I claim: I Y

1. In the process for separating ammonia and hydrogen sulphide from gases containing same by washing the gases with liquors conresidual gases in, two stages, thereby separating from the gases in the first stage such a part ofthe hydrogen sulphide content, that f in the second stage for one molecule of hydrogen sulphide more than two molecules of ammonia are available by the addition of such a quantity of sulfurous acid to the rst washing stage as is about chemically equivalent to the amount of hydrogen sulphide present in the gases and b`y adding the separated ammonia by the second washing stage.

3. In the process for separating ammonia and hydrogen sulphide from gases containing same by washing the gases with liquors containing ammonium polythionate and ammonium thiosulfate, the steps which comprise separating from the gases at least `a part of their ammonia content, washing the residual gases in two stages, thereby separating from the gases in the first stage such a part of the hydrogen sulphide content, that in the second stage for one molecule of hydrogen sulphide more than ltwo molecules of ammonia are available by the addition of such a quantity of sulfurous acid to the irstwashing stageas is about chemically equivalent to the amount of hydrogen sulphide lpresent in the gases and by adding the separated ammonia to the second washing stage, and exchanging the washing liquors obtained in the two stages.

f1. Process according to claim 1 consisting in effecting the separation of ammonia and hydrogen sulphide under superatmospheric pressure.

5. Process according to claim 2 consisting in effecting the separation of ammonia and hydrogen sulphide under superatmospheric pressure.

6. Process according to claim 3 consisting in effecting the separation of ammonia and hydrogen sulphide under superatmospheric pressure. y

In testimony whereof I have hereunto set my hand.

CHRISTIAN HANSEN.

taining ammonium` polythionate Vand ammonium thiosulfate, the steps which comprise separating from the gases atleast a part of their ammonia content, washingthe Y residual gases in two stages thereby separating :from the gases in theV first stage such 'a part of the hydrogen sulphide content that yin the second stage for one molecule of hydrogen sulphide more than two molecudes of ammonia are available by adding the separated ammonia to the second washing stage.

2. In the process -or separating ammonia and hydrogen sulphide from gases containing same by washing the gases with liquors containing ammonium polythionate and ammonium thiosulate, the steps which comprise separating from the gases at least a y part of their ammonia content, washing the 

